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No Further Action Required Request Report <br /> Mountain House Development Site#6 September 15,2011 <br /> from 2,260 to 2,560 milligrams per liter(mg/L), which did not exceed the TDS WQO of <br /> 3,000 mg/L. <br /> Based on the results of the investigation, SAIC recommended additional step-out borings to <br /> delineate the extent of affected soil and groundwater; and the Central Valley RWQCB concurred <br /> I with the findings and recommendations (Central Valley RWQCB, 2008b). <br /> 2.3 SOIL AND GROUNDWATER INVESTIGATION, 2010 <br /> SAIC advanced 15 borings (SB-30 through SB-44)using a Geoprobe�' 7822DT direct-push rig <br /> ' between November 9 and November 18, 2009, to total depths between 25 to 35 feet bgs in <br /> accordance with a 2007 work plan (SAIC, 2007). Hydrocarbon-affected soil was encountered in <br /> I SB-30, SB-32, SB-36, and SB-39 through SB-43. <br /> TPHc was detected above ESLs in two soil borings. The highest concentrations of TPHc, <br /> ethylbenzene, and PAHs were detected in the sample from boring SB-39 at 20 feet bgs <br /> I (6,900 mg/kg, 0.051 mg/kg, and 2-methylnaphthalene at 4.5 mg/kg, respectively). <br /> SAIC collected groundwater samples from seven borings for laboratory analysis. TPHd was not <br /> detected above ESLs in any of the groundwater samples submitted. BTEX constituents were not <br /> ' detected above ESLs or WQOs in any samples. Benzo(a)pyrene was detected above WQOs in <br /> three groundwater samples with a maximum detection of 0.004 µglL in the sample collected <br /> from S13-41. TDS were measured at 2,190 mg/L in the sample collected from SB-41. No other <br /> PAHs were detected above WQOs or PAHs in any groundwater samples. <br /> Additionally, a water sample was collected from the nearby Foster Well, which is currently in <br /> use by a nearby residence. The Foster Well is located up gradient of the boring SB-19 (advanced <br /> during the 2008 investigation). The sample from the Foster Well (FosterWell-1) did not contain <br /> concentrations of TPHd, BTEX, or PAHs exceeding the laboratory reporting limits, WQOs, or <br /> ' ESLs. Various water-quality parameter analytical results from the Foster Well, such as General <br /> Minerals and TDS, exceeded screening levels. <br /> Based on past experience at HPP-BTR project sites, attenuation of crude-oil constituents in <br /> ' groundwater occurs a very short distance from HPP-BTR facilities; and it is improbable that <br /> affected groundwater extends from the Site as far as the Foster Well. In addition, the Foster <br /> Well is located up gradient in relation to the areas of known affected groundwater,which <br /> indicates that it is unlikely to be affected by crude oil related to the former OVP or TAOC <br /> pipelines. <br /> SAIC evaluated the results of the investigation and concluded there are two areas of affected soil <br /> and groundwater that have been delineated. Additionally, the extent of affected groundwater is <br /> likely stable or decreasing, and concentrations of dissolved constituents will gradually decrease <br /> as the petroleum hydrocarbon mass is depleted. Groundwater samples submitted for General <br /> ' Minerals analysis had detections above the minimum WQOs or ESLs, and are thus considered to <br /> contain certain taste- or odor-producing substances in concentrations that cause nuisance or <br /> adversely affect beneficial uses. These exceedances indicate that the uppermost water-bearing <br /> ' zone is not suitable for drinking water use. <br /> SAIC recommended performing a human health screening evaluation (HHSE) as a further step in <br /> the process of moving the Site toward NFAR status. The Central Valley RWQCB concurred <br /> 3 SAII: <br />